The 1965 floods of the South Platte River basin swept through the Front Range and Eastern Plains of Colorado leaving 21 dead, 250,000 acres inundated and $540 million in damage. Heavy rains on four consecutive days in three different areas of the South Platte basin caused flooding from Plum Creek, south of Denver, to the Nebraska state line.

The storms took place over the Greeley-Sterling area on June 14-15, the Plum Creek and Cherry Creek basins on June 16 and the Kiowa and Bijou Creeks near Deer Trail on June 15 and 17, causing floods in 15 counties. Warm, humid air from the Gulf of Mexico had mixed with a cold pattern from the Northeast, and the turbulent stew stalled along the Front Range for 23 days, packing in moisture that would eventually spawn the tremendous rainfall on June 16.

The main flood through the metro Denver area on June 16 originated in the Plum Creek basin after 14 inches of rain fell south of Castle Rock. By the time the runoff reached Sedalia, the water widened East Plum Creek from 3 feet to nearly a mile. The wall of rushing water swept away trees, houses, cars and livestock before plunging into the South Platte below Littleton.

The violent waters reached Littleton, Englewood and Denver at about 8 p.m., destroying 120 houses and damaging 935. Two hundred eighty mobile homes were lost and 16 bridges in Denver were demolished.

After the flood, Chatfield and Bear Creek reservoirs were built to control storm waters.